Until this week, Scott Prouty’s only bout with fame came when he dived into a canal in Florida and saved a woman from drowning. Like many Americans, the Boston area native held down working-class jobs, ran into some financial trouble and remained generally anonymous.

But not many Americans are responsible for nearly bringing down a presidential campaign. And Prouty, 38, has now outed himself as the man who shot the infamous “47 percent” video showing Mitt Romney dismissing President Obama’s supporters during a private fundraiser, the single event that more than anything else may have ruined Romney’s shot at the presidency.

“I was behind this whole thing,” Prouty, who now lives in Florida, said as he revealed on MSNBC’s “The Ed Show” on Wednesday night that he had secretly filmed Romney’s comments while tending bar at the $50,000-per-plate event.

Prouty’s unveiling, if nothing else, exposed him to the scrutiny that comes with being one of the most influential, if unknown, figures in the presidential campaign that gave Obama a second term. Speaking in firm, declarative tones with a slight Boston accent, Prouty presented himself as someone not motivated by politics, saying he is a “registered independent” who tends to vote Democratic but “didn’t go there with a grudge against Romney.”

Yet voter-registration records show that Prouty registered as a Democrat in 2002, and election officials said he has maintained that party affiliation. His former Twitter account is full of populist and political messages, including several criticizing Romney or former GOP vice-presidential candidate Paul Ryan and another blasting National Rifle Association chief executive Wayne LaPierre as “an evil man.” Prouty attended Obama’s second inauguration and also told MSNBC’s Ed Schultz he was “proud to call him my president.”

In Prouty’s native Massachusetts, where he grew up in the working-class community of Braintree and attended Northeastern University, his father, Kenneth Prouty, declared he was “very proud of my son.’’

“Everything he said pretty much rings true,’’ the senior Prouty said in a brief telephone interview. “Mitt Romney made his bed. It wasn’t really Scott doing it; it was Mitt Romney doing it. It kind of showed his true colors.’’

He said his son “was kind of sticking up for the American public as far as I’m concerned. The average person who couldn’t be there to hear what was going on.’’

At the time, Romney’s remarks — made at a May 17 fundraiser in Boca Raton, Fla., at the home of private-equity manager Marc Leder — riveted the political world. Obama backers will vote for the president “no matter what,’’ the Republican candidate said in a video that Prouty leaked to Mother Jones magazine’s Washington bureau chief David Corn, adding that he does not “worry about those people.”

In a recent interview with “Fox News Sunday’s” Chris Wallace, the former Massachusetts governor admitted that the comments’ damage was severe. “That hurt. There’s no question that hurt and did real damage to my campaign,” Romney said.

But on Thursday, Prouty’s unveiling landed with a collective thud for a Republican Party and conservative movement that seems to want to move beyond the man who lost what many considered a winnable election. Former Romney campaign staffers declined to comment, as did others in the Republican Party.

Ironically, it was Romney’s recent emergence from his self-seclusion after the election — he is also scheduled to speak Friday at the CPAC convention of conservative activists — that Prouty indicated was what motivated him to finally come forward.

“Romney came out, again, on Fox News,’’ Prouty told Schultz. “He’s calling the president Nero. He’s saying his words were twisted. He’s blaming the media. . . . He’s sitting in his mansion in San Diego somewhere and giving interviews and calling the president names.”

After the May fundraiser, Prouty said he struggled for two weeks deciding whether to release the video and risk his career. He worried about losing his job or getting sued; Florida laws prohibit the recording of anyone without consent.

He decided he had an obligation to go public, adding this jab at Romney: “I don’t think he has any idea what a single mom, you know, taking a bus to work, dropping her kid off at day care that she can barely afford, hopping on another bus — you know, the day in, day out struggles of everyday Americans. That guy has no idea, no idea.”

With Romney having mostly dropped out of the political zeitgeist, pretty much the only remaining curiosity Thursday was about Prouty. Little information was available, with numerous family members and friends not responding to requests for comment.

Court records show that that Internal Revenue Service in 2006 secured a more than $15,000 federal tax lien against Prouty for unpaid taxes from 2000 and 2002. It was unclear whether Prouty has repaid the money.

The records also show that an insurance company obtained a more than $5,700 default judgment against Prouty and a woman named Susan Dibella in 2009 in Broward County, Fla., court. Attorneys in the case did not return telephone calls, and a telephone number listed for Dibella had been disconnected.

In another bout with the court system, Prouty in 2011 filed a sexual-harassment lawsuit against Gulfstream Park Racing Association, which runs a number of horse-racing casinos in South Florida. According to the lawsuit, Prouty worked at a Gulfstream facility for 31/2 years as a bartender but was passed over for promotions in favor of female employees who were “having sexual relations with management.”

Prouty was fired, and the case was dismissed after mediation, court records said.

In 2005, while working for an auto dealership, Prouty and two co-workers were honored for saving the life of a woman trapped underwater in her vehicle after it plunged into a canal along Interstate 75. The Weston City Commission resolution said Prouty dived into the water, cut the woman out of her seat belt and kept diving back in after noticing a child safety seat, although there was no child in the car.

Prouty was joined on Schultz’s show by Charles Kernaghan, an international labor rights activist and the director of the Institute for Global Labour and Human Rights, who has become a friend.

The labor activist produced a report in late September, titled “Betting Against American Workers” that used information from Prouty’s video to attempt to tie Romney to poor labor practices in China. Prouty contacted Kernaghan after he saw the report online and the two struck up a friendship, although Prouty remained anonymous.

“We talked on the phone and were similarly passionate” about the treatment of workers, Kernaghan said. The two men attended Obama’s second inauguration together in January.

James Carter IV, a former researcher for Corn who now operates his own research firm, shed more light in a telephone interview Thursday on how the 47 percent video was made public. Carter, who is former president Jimmy Carter’s grandson, said Prouty had anonymously posted a muddied clip of Romney at the same fundraiser that he found especially galling. Romney was speaking about a visit to a factory in China during his days at Bain Capital.

The clip did not gain traction online, but Carter — who describes himself as an opposition researcher — had been scouring the Web for videos of Romney with the hope of finding something that he might be able to use against Republicans. He saw Prouty’s clip, which had been posted under the pseudonym Anne Onymous670. Carter noticed that he was being followed on Twitter by a person using the same pseudonym and struck up a conversation.

“He followed me first, and I sent him a direct message. It was a mutual,” Carter said.

Prouty told Schultz that he connected with Carter after reading a story by Corn about an investment that Bain Capital made in a Chinese firm that Carter had helped research.

Jerry Markon covers the Department of Homeland Security for the Post’s National Desk. He also serves as lead Web and newspaper writer for major breaking national news.

Krissah Thompson began writing for The Washington Post in 2001. She has been a business reporter, covered presidential campaigns and written about civil rights and race. More recently, she has covered the first lady's office, politics and culture.

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